A new analysis from Rutgers Health suggests that one of the simplest measurements in medicine — a tape measure around the waist — identifies obesity-related health risk about as well as a considerably more elaborate new framework.[1]
The study, published in JAMA Network Open, compared several ways of screening for obesity against a highly accurate reference method for body fat, using data from 1,900 U.S. adults aged 20 to 59 in the National Health and Nutrition Examination Survey.[1][2]
What the researchers were testing
The comparison target was a recently proposed obesity framework developed by a multidisciplinary expert group. That approach combines four measures: BMI, waist circumference, waist-to-height ratio and waist-to-hip ratio.
The newer framework did flag a larger number of people as having excess body fat. But flagging more people is not the same as flagging them accurately, and that distinction is where the Rutgers analysis lands.[1]
Simpler measures held their own
Using either BMI or waist circumference alone produced a better balance between correctly identifying people with obesity and avoiding false-positive diagnoses than the four-measure framework did. Waist circumference on its own performed nearly as well as any combination tested.[1]
That has practical consequences. Hip circumference — required for one of the ratios in the proposed framework — is rarely recorded in a routine clinical visit. Waist circumference is far easier to take and already appears in a growing number of clinical guidelines.[1]
“Our findings show that you don’t necessarily need multiple complex measurements to identify obesity-related health risks,” said lead author Aayush Visaria of Rutgers. “A waist measurement provides much of the information needed and is feasible for clinicians and patients alike.”[1]
The limitation of BMI the study exposed
When BMI was used by itself, it failed to identify a substantial number of people who met body-fat criteria for obesity. This is a longstanding criticism of the index rather than a new one, but the analysis quantifies it in a nationally representative sample.[1]
BMI is a ratio of weight to height. It cannot distinguish muscle from fat, and it says nothing about where fat sits in the body. Two people with identical BMI can have very different amounts of abdominal fat — and very different metabolic risk as a result.
Why the location of fat matters
Fat stored around the abdomen behaves differently from fat stored under the skin of the hips and thighs. Visceral fat around the organs is more metabolically active and more strongly associated with insulin resistance, dyslipidemia and cardiovascular disease.
Waist circumference is a crude proxy for that compartment, but a useful one — which is why it can carry information BMI alone does not, without requiring imaging or specialized equipment.[1]
What this means for an ordinary check-up
Visaria offered a deliberately unclinical version of the advice: pay attention to needing to loosen your belt or move up a trouser size. Clothing size is not a proper waist measurement, but it can be an early signal of rising body fat.[1]
A correct measurement is taken with a flexible tape at the top of the hip bone, level and snug without compressing the skin, at the end of a normal exhale. Taking it at the same point each time matters more than the absolute number on any single day.
The researchers suggest wider routine use of waist measurement could make obesity screening more practical while still catching many people at elevated risk of diabetes, heart disease, stroke and some cancers.[1]
Limitations
This is a cross-sectional accuracy comparison, not an outcomes study: it tested how well each method identified excess body fat, not which method best predicts who later develops disease. That is a different and harder question.
The sample was restricted to U.S. adults aged 20 to 59, and healthy waist thresholds differ by sex and by ancestry — cut-offs recommended for East Asian populations are lower than those commonly used in Western guidelines. No single number applies everywhere.
| Aspect | Detail |
|---|---|
| Institution | Rutgers Health, with Rutgers Robert Wood Johnson Medical School |
| Data source | 1,900 U.S. adults aged 20–59 from NHANES |
| Journal | JAMA Network Open, 2026;9(8):e2627738 |
| Methods compared | BMI alone; waist circumference alone; BMI + waist; a four-measure expert framework |
| Key result | Waist circumference alone performed nearly as well as the complex framework |
| BMI weakness | Missed a substantial number of people meeting body-fat criteria for obesity |
| Practical barrier | Hip circumference, needed by the framework, is rarely measured in routine visits |
| Study design limit | Accuracy comparison against body-fat reference, not long-term disease outcomes |
| Everyday signal | Needing to loosen a belt or size up trousers may be an early warning |
References
- ScienceDaily / Rutgers University, “Your waist size may reveal health risks BMI misses,” 29 August 2026.
- Visaria A, Corsi D, Patel D, Kesavarapu K, Halm EA, Carson J, Setoguchi S. “Lancet Definition vs Other Criteria for Obesity Diagnosis in Adults.” JAMA Network Open. 2026;9(8):e2627738. DOI: 10.1001/jamanetworkopen.2026.27738
